More than 90% of the cancer death cases are caused by cancer metastasis, where few tumor cells shed from primary tumor, circulate in the peripheral blood and finally dock and proliferate in another organ. The most effective approach for metastasis diagnosis is by the detection of circulating tumor cells (CTCs), so called “liquid biopsy”. However, identifying a few CTCs amongst billions of blood cells is extremely challenging, as the CTC morphology is similar to those of blood cells, and due to the heterogeneity between CTCs.
It has been found that the electrical properties of tumor cells are different from that of normal blood cells. This difference in electrical properties is mainly due to the difference in cell membrane impedance, or in particular, in cell membrane capacitance. Multiple cancer cell lines have displayed a much higher membrane capacitance than normal blood cells. This finding brings the promise of isolating viable individual CTCs, which will enable further phenotyping and genotyping of CTCs, as well as improved clinical diagnosis and therapy.
As the whole cell membrane impedance is also dependent on cell size; measurement of absolute cell membrane impedance may lead to incorrect cell identification, as this cell size can be rather heterogeneous, especially for cancer cells. For example, a big monocyte may have the same cell membrane impedance as a small cancer cell.
So there is a need for a method to identify CTC's in blood using cell impedance measurements with a high efficiency and accuracy.